Backlight unit

Abstract

A backlight unit includes a light source unit which generates and emits light for displaying an image; a light guide plate which guides the light from the light source unit toward a display panel which displays the image with the light, the light guide plate including: a light incident surface which faces the light source unit and through which the light is incident into the light guide plate, an upper surface through which the light is emitted from the light guide plate to the display panel, and a lower surface which opposes the upper surface; a reflective sheet which faces the lower surface of the light guide plate; and an angular filter which transmits light of a predetermined angle to the light incident surface of the light guide plate, the angular filter between the light source unit and the light incident surface of the light guide plate.

What is claimed is: 
     
         1 . A backlight unit comprising:
 a light source unit which generates and emits light for displaying an image;   a light guide plate which guides the light from the light source unit toward a display panel which displays the image with the light, the light guide plate comprising:
 a light incident surface which faces the light source unit and through which the light is incident into the light guide plate, 
 an upper surface through which the light is emitted from the light guide plate to the display panel, and 
 a lower surface which opposes the upper surface; 
   a reflective sheet which faces the lower surface of the light guide plate; and   an angular filter which transmits light of a predetermined angle to the light incident surface of the light guide plate, the angular filter between the light source unit and the light incident surface of the light guide plate.   
     
     
         2 . The backlight unit of  claim 1 , wherein the angular filter comprises a first refractive index layer and a second refractive index layer having different refractive indices from each other and alternately disposed with each other. 
     
     
         3 . The backlight unit of  claim 2 , wherein each of the first refractive index layer and the second refractive index layer of the angular filter has a thickness in a range from about ⅛ to about ½ of a light wavelength incident to the angular filter. 
     
     
         4 . The backlight unit of  claim 3 , wherein
 the first refractive index layer has a refractive index in a range from about 1.1 to about 1.4, and   the second refractive index layer has a refractive index in a range from about 1.4 to about 1.8.   
     
     
         5 . The backlight unit of  claim 1 , wherein the light source unit, the light guide plate and the angular filter disposed therebetween have a monolithic structure. 
     
     
         6 . The backlight unit of  claim 1 , wherein the light source unit comprises:
 a light emitting diode chip which generates and emits the light;   a circuit board on which the light emitting diode chip is disposed; and   a light transmitting sealing member which seals the light emitting diode chip on the circuit board.   
     
     
         7 . The backlight unit of  claim 6 , wherein
 a portion of the light transmitting sealing member is disposed between the light emitting diode chip and the angular filter, and   the light source unit further comprises a light conversion member embedded within the portion of the light transmitting sealing member.   
     
     
         8 . The backlight unit of  claim 7 , wherein the light conversion member embedded within the portion of the light transmitting sealing member is between the light emitting diode chip and the angular filter. 
     
     
         9 . The backlight unit of  claim 8 , wherein the light conversion member comprises:
 a red conversion portion which absorbs a blue light and emits a red light; and   a green conversion portion which absorbs a blue light and emits a green light.   
     
     
         10 . The backlight unit of  claim 6 , wherein the light source unit further comprises a reflective layer between the circuit board and the light emitting diode chip. 
     
     
         11 . The backlight unit of  claim 1 , comprising a first light output pattern on the upper surface of the light guide plate. 
     
     
         12 . The backlight unit of  claim 11 , wherein the first light output pattern comprises a lenticular lens. 
     
     
         13 . The backlight unit of  claim 1 , further comprising a second light output pattern on the lower surface of the light guide plate. 
     
     
         14 . The backlight unit of  claim 13 , wherein the second light output pattern comprises an asymmetric prism. 
     
     
         15 . The backlight unit of  claim 14 , wherein the asymmetric prism of the second light output pattern on the lower surface of the light guide plate comprises:
 two oblique sides each extending from the lower surface of the light guide plate, and   among the two oblique sides, the oblique side closer to the light incident surface of the light guide plate having an angle in a range from about 75 degrees to about 90 degrees with respect to the lower surface of the light guide plate.   
     
     
         16 . The backlight unit of  claim 15 , wherein
 the light guide plate further comprises a light opposing surface which opposes the light incident surface,   the asymmetric prism of the second light output pattern is provided in plurality along the lower surface of the light guide plate, and   a density of the asymmetric prisms increases as a distance from the light incident surface toward the light opposing surface increases.   
     
     
         17 . The backlight unit of  claim 11 , further comprising a light re-guide layer on the first light output pattern, wherein the light re-guide layer reflects light emitted from the first light output pattern toward the display panel back to the first light output pattern. 
     
     
         18 . The backlight unit of  claim 17 , wherein a refractive index of the light re-guide layer is in a range from about 1.40 to about 1.50. 
     
     
         19 . The backlight unit of  claim 1 , wherein the reflective sheet comprises a plurality of prisms having symmetric or asymmetric cross-sections, wherein the plurality of prisms reflects light emitted from the lower surface of the light guide plate toward the reflective sheet back to the light guide plate. 
     
     
         20 . A backlight unit comprising:
 a light source unit which generates and emits light for displaying an image;   a light guide plate which guides the light from the light source unit toward a display panel which displays the image with the light, the light guide plate comprising:
 a light incident surface which faces the light source unit and through which the light is incident into the light guide plate, 
 an upper surface through which the light is emitted from the light guide plate, and 
 a lower surface which opposes the upper surface; 
   a reflective sheet which faces the lower surface of the light guide plate; and   a light re-guide layer on the upper surface of the light guide plate, wherein the light re-guide layer reflects light emitted through the upper surface of the light guide plate toward the display panel back to the light guide plate.